Relation-indicator.



E. e. BAILEY. RELATION INDICATOR.

APPLICATION FILED MAY I3, 19M.

Patented Mar. 5, 1918.

3 SHEETS-SHEET 1 E. G. BAILEY.

RELATION INDICATOR.

APPLICATION FILED MAY18.\914.

Patented Mar. 5, 1918.

g. SHEETS-SHEET 2.

E. G. BAILEY.

RELATION INDICATOR.

APPLICATION FILED MAY 18. 1914.

Patented Mar. 5, 1918.

3 SHEETS-SHEET 3 Un -ran snares PATENT onnroa.

ERVIN G. BAILEY, OF NEWTON HIGHLANDS, MASSACHUSETTS, ASSIGNOR TO BAILEYMETER COMPANY, A CORPORATION OF MASSACHUSETTS.

RELATION -INDICATOR.

Specification of Letters Patent.

Patented Mar. 5, 1918.

Application filed May 18, 1914. Serial No. 839,320.

To all whom it may concern:

Be it known that I, ERVIN G. BAILEY, a citizen of the United States,residing in Newton Highlands, in the county of Middlesex and State ofMassachusetts, have invented an Improvement in Relation-Indicators, ofwhich the following description, in connection with the accompanyingdrawings, is a specification, like letters on the drawings representinglike parts.

The present invention relates to a relation-indicator, and is embodiedin an instrument adapted to be used in conjunction with a powerproducing or using apparatus for the purpose of continuously showingwhether or not the condition of best efficiency exists at any and allrates of output and also showing the nature of the departure from thecondition of best efficiency, should such take place.

The instrument embodying the invention consists of a plurality ofdevices or meters which may be of any suitable known type, such aspressure gages, flow meters, watt meters, etc, each having an index orpointer that is moved in a definite manner in response to changes in themagnitude of one of the factors which is essential to the operation ofthe power producing or using ap.

paratus to which the invention is applied; the novelty of the inventionlying in the proper arrangement of the indiccs with re lation to eachother, together with the requirement that atleast one of the devices isprovided with means whereby it shows a fictitious reading so to speak,instead of showing the reading that would normally be given should asimilar device be used to measure the factor alone. Furthermore, thisfalse or fictitious reading, thus obtained is not. readily useful initself as an absolute measure of the factor to which it responds,

but only serves to show whether or not the proper relation existsbetween this and some other factor which factors are coactive in thesame apparatus. This proper arrange mentof the several indices and themodifying of one or more of the several devices, so that least one ofthe devices will give a fictitious reading is herein termed thecorrelation of the devices and is brought about for the purpose ofmaking all of the indices show the same reading at any and all rates ofoutput of the apparatus so long as the different factors hold the properrelation to each other.

Examples of what I regard as active factors in a power producing orusing apparatus within the scope of my invention, are the flow of air tosupport combustion, the flow of steam and the flow of the products ofcombustion in the case of a steam generator, the flow of steam and otherfluids in a turbine, engine or pump, the flow of electricity (which forthe purposes of my invention may be regarded as a fluid) in an electricgenerator, or in an electric motor, the flow of liquid fuel, or ofgaseous fluid, to a power generator, the pressure of such fluids, thespeed of the moving parts of such an apparatus and the heat of thefluids in such an apparatus.

When I refer to the relation that does or should exist between twovariable active factors, I do not mean merely the simple ratio thatexists at any one particular rate of output or under one set ofconditions, but I use the word in its broad sense as applied to aphysical law which exists between two factors whatever the intensity orvalue of one may be. All physical laws may be expressed by means ofmathematical equations or formulas, although many of them are socomplicated that in practical engineering work the relation is shown byplotting the factors and showing the relation as a. graphic curve.

For example, if we desire to indicate the condition of desiredeiiiciency of an electric generator in which the input is the steamconsumed and the output is the kilowatts developed, we know thatthroughout the range of output the relation of these two factors is suchas to be capable of expression by a mathematical equation in which wemay call the steam input a? and the kilowatt output The difficulty ofindicating the relation between these two factors as and y in anyapparatus is that they do not bear to one another any simplerelation noreven a constant ratio. That is is not to 3 as 1 is to 2 or as 2 is to 3,but the relationis much more complicaten, in fact it may be expressed hythe equation :c:f +a where 7 is some function of y and a. 1s a constant.That function may be a multiple or a divisor words, a perfectly definiterate of steaminput m is required to produce a given rate of electrical.output 1 For each. different value of 1, :0 will have a correspondingand definite value in accordance with the equation, or water rate curveof the turbine, so long as the desired operating 'efficieney exists. Butshould some change take place in the mechanical adjustments or theoperating conditions of the turbine that would affect its efliciency,then a different relation or equation would exist between m,

and y. The, purpose. of the present invention isto. show Whether ornot'the" desired relation; exists. between two factors corresponding to0 and y, in other words, whether or not their relative values conform tothe proper equation, whatever their actual values or the rate of outputof the apparatus maybe. This object is accomplished in. my presentinvention by providing separate devices or meters that will respond toeachof the factors respectively, such as m and 1 and also to providemeans to so correlate the device that indicates the value of a; with thedevice that indicates the value of 'y, that the index or pointer of them device will coincide with andshow'the same reading as the index of they device, whatever may be the rate of output of the apparatus as awhole, so that as long as :0 and i have values that satisfy the equationdetermining their relation, the coincidence of the indices thusshowslthat .the apparatus'is working at its best efficiency; and a lack.of such. coincidence will not only 'sh-owthat the proper relation forbest efficiency does not exist, but it will show the nature and probablecause of the inefficiency.

In like manner there isa perfectlydeiinitev and fixed relation betweenthe rate of input and the rate of output or between any other similaractive factors in all kinds of power producing or using apparatus, maccordance with the physical law existing; between the .two' factors. IThe foregoing statementholds trueffor all rates of output of theapparatus nomatter how. complex the relation;betweendthe factors may be,solong as 'the'mechanical and controllable operatmg conditions remainnormal 111. accordance. with certain. standards. 1 The. -objectofifthisf in. ventlonis toprovide anundicator that 'wiill' attendantcan. know instantly whether .or

i notlthel. desired efficiency of the. apparatusis' being maintained,and if not, What controllableoperating conditions are at fault and whatshould be done to remedy them.

The instrument embodying my invention, therefore, consists of aplurality of mechanical devices, each of which is operated upon by aforce which is a function of one of the factorsacombined with suitablemeans cor relating the said devices, so that any de- .parture. from thedesired relation. between the several factors at any and all rates ofoutput is indicated at a single reading of the indices. The correlationabove described accomplishedby suitably making, select iitg, arranging,modifying, or adjusting the mechanical devices or meters so that theindex or pointer of one, two or more of them will always show the samereading as the index or pointer of the other one when. the operatingforces hold the relation to each other which ought to exist at the rateof out-.

put which is being maintained, and this will also be true" for any otherrate of output which may happen to exist in the normal operation of theapparatus.

I am aware of the fact that measuring in.- struments operating bypressure differences or other varying active factors entering into theoperation of an apparatus have been used. in the attempt to indicate theefficiency condition of said apparatus. So far as I have seen, however,the instruments which have been. devised for this purpose prior to myinvention indicatesimply the actual values. of the pressure differenceor other factors, or the actual value of the ratio which exists at thetime of observation. As above stated, however, the desired result,attained. by my invention is not accomplished by showing the: actualvalues of .the factors or what actual relations exist between them,butsh'ows at a single reading whether ornot the relation correspondingto the condition of best efficiency is the existing relation at the.time of observation regardless of what the rate of. output may be. Thisentirely new and practicable result isobtained in accordance with myinvention by the means included in the embodiment ofithe. invention.correlating the devices operated by the. active factors.

Instruments of various forms all of which embody the generic. featuresof my inventionv can. be: devisedffor use in. connection with anyapparatus such as I. have referred to. above; and for the. pin-pose. ofillustrating the invention. I have .1 herein shown aninstrinnent.especiallyadapted for use. in. connection. Wlfllf. arsteamboiler and' have also'lshown. several. modifications whichv may bereadily adapted for-other uses.

"It. is; to be. understood that: the specific con structionandarrangement of. the several "rechanical ldeviccs or meterswhiclrare.associated .in carrying out. the .present invention form no part oftheinvention and these devices may be of any known form or character.

Figure 1 is a vertical section, partly in elevation of an instrumentembodying my invention, the said instrument being especially adapted foruse in connection with a boiler plant in which the factors used in theoperation of the instrument are the rate of flow of air, the rate offlow of steam, and the fuel bed resistance; Fig. 2 is a similar view ofan instrument in which the associated devices are an electric meter, asteam flow meter, and a water meter; and Fig. 3 is a view illustrating acombination of U- tube gages as the devices which may be utilized incarrying out my invention.

In Fig. 1 I have shown the instrument as provided with a chart 1, inconjunction with several indices, in this instance pens 2, 3, and 4, thesaid chart being in view so that it constitutes an indicator scale aswell as a recording means to afford a permanent record of conditions.This instrument is especially adapted for use in connection with a steamgenerator burning solid fuel, in which the flow of air should bear acertain determinable relation to the flow of steam throughout the entirerange of output, while the resistance of the fuel bed should also hear adeterminable relation to the rate of flow of air when the fuel bed is inthe condition of best etliciency.

Ihave shown the instrument chosen to illustrate this invention, ascompletely equipped with means for showing the fuel bed condition aswell as the condition which depends upon the right relation between therate of flow of air and the rate of flow of steam. The presentinvention, however, is embodied in the combination and means forcorrelation. of the devices which show the departure from the desiredrelation between the rate of flow of steam and the rate of flow of air,and involves the devices operating the pens 2 and 3, the constructionand arrangement of the pen 4, being set forth in a prior patent, N umber1,153,414, granted to me September 14-, 1915.

The pen 3 which moves in response to the rate of flow of steam isoperated through a beam 18 pivoted at 14 and acted upon by a bell 15which is arranged to receive pressures on opposite sides through thepipes 16 and 17 which lead from the respective sources of pressure. Thebell 15 is sealed in a liquid and rises or falls in response todifferences in pressure, the action of the device being modified bymeans of a displacing member 18 part of which extends into a liquid 19whereby a state of equilibrium is brought about. The pen 2 which movesin response to the rate of flow of air is operated upon by a similardevice comprising a liquid scaled bell 20 receiving pressures onopposite sides, through the pipes 21 and 22, and the said bell isattached to a beam 23 pivoted at 38 and balanced by a weight 24. Thisbell is similarly associated with a displacing mem ber 25 which extendsinto a liquid contained in a receptacle 26, and quilibrium is therebybrought about as described in connection with the device which operatesthe pen 3.

By suitably shaping the displacing member 18 according to the law of theflow of steam through an orifice, or other corresponding means, themotion of the pen 3 can be made to follow any desired relation. to therate of flow. It is desirable that this pen motion should be in directproportion to the rate of flow so that the chart records may be easilymeasured. In a similar manner the shape of the displacing member 25constitutes the means correlating the devices and is made in accordancewith the relation between the two factors, viz: the rate of steam flowand rate of air flow, or the pressure differences which are functions ofthe same, as empirically determined for all rates throughout the rangeof operation; so that the pen 2 will always lie immediately in front ofthe pen 3 and thereby show and record the same reading as pen 3 when therate of air supply is as desired, regardless of whether the rate ofsteam output is great or small; and in response to any changes in therate of steam output the pens 2 and 3 will move in unison so long as theproper relation is maintained.

The general law governing the relation be tween steam output and thepressure difference which is a function of the air supply, may be usedin designing the shape of the displacing member 25 as a standard part ofthe instrument to be applied to any boiler. Then suitable adjustmentsare provided for by affording means for changing the length of themoment arm through which the displacing member 25 acts, the normal levelof the liquid in the receptacle 26, the density of the liquid, and theposition of the balancing weight 39, in accordance with the empirical.determinations in any individual. boiler, so that the pens 2 and 3 willgive the same reading, so long as the desired conditions exist regardlesof the rate of output. It is obvious, however, that the chart or itsequivalent is not an essential. element to the instrument, for withoutany chart, scale, or any background whatever, a person can see whetheror not the two pens 2 and 3 are together.

The usefulness of such an instrument is greatly enhanced if it has, inaddition to means for performing the functions above described, furthermeans. for recording the conditions existing in the operation ofanapparatus at all times, whether or not the desired relation isdeparted from. The instrument shown in Fig. 1, for example, is capableof recording .t1 1e .departure and ex tent of departure irom the desiredcondition throughout a given period ofopel'a ion. Th pen- 8, which showsa measure of the rate of steam output is supplied with ink of one color,while the pen 2 is supplied with ink of a differentcolor. So long as thedesired a relation exists between the rate of air supply and the rate ofsteam output, these two records coincide, and make a" characteristicrecord of a subst'antially' single line of blended color. It is obviousthat any other characteristic markings 'may be used, such as may befound convenient. This results in the decided advantage that theinstrumentshows on the record, not only the time whenthe desiredrelation was not maintained {but also'to what extent the relation wasdeparted from and which of'the factors was excessive or deficient atthattime.

Y The pen at, in conjunction witht'he line 12 onthe chart 1 serves toindicate the fuel bed condition and is readily incorporated, as shown,in the instrument, sofas to give" a complete record. The bells 7 and 8'may be immersed in the-sameliquid which seals the bell 20, the saidbellsbei-ng hung from-the beam 6 and "acted on by p'ressures conductedthrough pipes 9, 10, and 11. The pen 4: is pivoted at 36 and actuatedthrough the arm 5' and the link 37 which is eonnected'to the beam 6.

In Fig. 2 I have shown: another-formof instrument embodying theinvention, this instrument being intended for use in connection withelectric generators in which there is,under con'ditions'of bestefficiency, a determinable relation between the rate of How of steam andthe kilowattoutput of the generator, This relation l-ikethe others ismore complex than a simple ratio and is usually expressed in the form ofa curve showing ihesteam consumption or water rate at dififerent loads;and in order, therefore, that any departure from the desired relationmay be readily shown by the instrument, the elements previouslydescribed in connection with Fig. 1, namely, the several deviceshaving'indices and the means for properly correlating them: constitutethe main elements of the instrument.

The indices, which are moved in response to forces which are functionsof the variable active tactors'of the apparatus, consist, in thisinstrument, of pointers 27 and 28,which are operated respectivelyby twodevices, viz: a steam flow meter 29 and a wattmeter 30, the steam flow:meter beingrepresentedas aninst'rument likeithat sh'owniandl describedin :connection with Fig. 1, except that the shape of thedisplacingmember may be ditfe'rentias required, for correlation, while thewattmeter can be 'of any suitable or usual type. In this instrument, theindices 'or pointersare shown as pivoted on a common axis at, Bl, @andadapted toatravel over :1,

graduated scale 32, which may, if desired, be graduated in terms ofkilowatt output. Assuming that the scale is so graduated, the steam flowmeter 29 is the element which is modified to effect-the correlation, s0that the position of the index 27 does not indicate the value of thepressure difference nor the rate of How of steam which is utilized tomove the index, but does indicate, in conjunction with the wattmeterindicator, any departure from the desired relation betweenthe steam flowand electrical output.

This instrument is further providedwith a third device comprising meansformeasuring-the water of condensation; and in the construction shown, aliquid meter of an improved weir type is employed and indicatedbythe'reterenee numeral The recessary correlation is eflectedby meansot'the shape of the weir openmgso that the pointer 34a The aperture orweir opening 01? this liq-' uid meter is through: a curved or warpedsurface 35, the curvature of which surlace is so designedand'constructed as to give any desired relation between ra-te of dischargeand head, as fully described in a" prior application for Letters" Patentof the-United States filed by me January 22, 191.3,Serial Number Tl-3,479. Any suitable meter, however,'may be used without departing fromthe present invention.

The instrument shown in Fig. 3' comprises a series of modified U-tu'bepressure gages 4-2, 43, and id, and the'sui-iace of the liquid in oneleg of eachtube constitutes the index and moves in response tovariations in ditference of pressures, the opposing pressures acting oneach tube together constituting a function of one of the associatedfactors. In this instrument the means correlatingthe factors is embodiedin displacing members 45, 4-6, and 47, of variable area or theequivalent of same which are inserted in the branches of the severaltubes so that the readings inthe tubes are not-necessarily in terms ofactual quantityor value but are the several gages regardless of 'their'actual value. These displacing members may be exchanged'for others, orothers addedgin accordance with the empirically determinedrequirementsot any individual case, thus forming an achustablefeature. The shapes of'the displacing members are determined trom'empiric'alobservation of the apparatus to which the instrument is to be applied,such as. a. steam generator,'in which the rate of steam output, the rateotgaseous-or liq-i 'uid fuel supply, rate of air supply, etc., are

the factors, the relation between which is under observation. Or if theinvention is to be applied to a pumping outfit in which the relationexists, the liquid in the several tubes will have the same motion andlie upon or near the same graduation of the scale.

It will be seen from the foregoing description that the basic featuresof my invention, which are found in all of the instruments chosen forpurposes of illustration, are the several mechanical devices or meterswith their respective indices; means wherebythe variable active factorsof apower producing or using apparatus are applied to said devicesrespectively; and means correlating said devices so that the relativeposition of the indices shows the existence or non-existence of adefinite relation between the several factors at all rates of output ofthe apparatus.

It is obvious that the specific construction and arrangement of theseveral devices or meters themselves, or the means correlating them, maybe such as will best suit the apparatus with which the instrument isintended a to be used; and any choice as to the specific mode ofoperation, form, or arrangement of said movable elements can be madewithout departing from the invention.

The term correlate is used herein as 'meaning not merely the placing oftwo pointers in juxtaposition, or in such location relative to oneanother that their readings may be read simultaneously, and comparedreadily as to the equality of reading or as to the difference betweenthe readings of the two, but involves further an organic or structuraladaptation or modification of the means or connections through which oneor more of the pointers responds to the factor-the condition of which isindicated by it, in such manner that the readings of each pointer arerelated to and significant in connection with the reading of some otherpointer, rather than as a correct indication of the factor for which itindicates, independently considered.

In an instrument made in accordance with this invention, it is notnecessary that any of the pointers or indicators should read correctlyfor the conditions of the factor to which it pertains, and in mostapplications of the invention, the effect of the correlating means willbe such that one or more of the pointers does not indicate correctly thecondition of the factor to which it pertains, if individuall considered,but only indicates the condition of the factor that-should prevail whenthe other factors are in such condition as to give the same or acoincident reading.

For purposes of clearly showing the utility and mode of operation of theinstrument embodying the invention, .its application to certainapparatus has been illustrated and described as a convenient example ofa use to which the instrument may be put; but it is to be understoodthat the said instrument is capable of other uses, and thatthe inventionis not limited to the particular use described.

lVhat I claim is:

1. A relation indicator to show whether or not the desired relationexists between two coactive factors in a power producing or usingapparatus consisting of a combination of two mechanical devices, eachhaving an index and each being actuated by one of the respectivefactors; and means correlating said devices whereby their indicescoincide whenever the desired relation exists between the two saidfactors.

2. A relation indicator to show whether or not the desired relationexists between two coactive factors in a power producing or usingapparatus, comprising a mechani cal device having an index; meanswhereby said device is operated by one of said factors; a secondmechanical device having an index; means whereby said second device isoperated by the second said factor; and

means whereby the second said device is modified in its action so thatits index will not respond in direct proportion to the factor operatingit, but in accord with the index of the first mentioned device so longas the desired relation exists between said factors, which relationcorresponds to the best efiiciency of the apparatus.

3. A relation indicator for use in connection with a power usingapparatus to show whether or not the desired relation exists between twocoactive factors one of which is power input and the other the work doneby the apparatus, which relation corresponds to the best etliciency atany rate of output, comprising a meter provided with an index andadapted to respond to the rate of power input; a second meter providedwith an index and adapted to respond to the rate at which work is done;and means modifying one of said meters so that instead of its indexresponding as a true measure of the operating factor it responds inexact accord with the other said index so long as the desired efficiencyof the apparatus exists whatever its rate of output may be.

at. A relation indicator for use in connection with a steam generatingapparatus to show whether or not the desired relation exists between twocoactive factors, such as rate of steam output and rate of air supplyfor combustion, which relation corresponds to the, best efficiency atany andall ra-tes of output, comprising a steam fiowimeterzprovided wlthan index and adapted to 1nd1cate the rate of steam outputya mechanicaldeapparatus, having in combinationsdevices eachprovided with an index;.;;means operating each index byone of said factors.; and means wherebyone of said factors-is caused to arbitrarily move its own index inaccordance with the law determining the relation between the factors,instead of in accordance with the actualvalue of the factor.

6. A relation indicator to show continuously. and at all rates ofoutput-,ofa steam generating apparatus the existence or nonexistence ofvthe desired :relationbetween the rate of steam output 1 from the boilerand the rateof supply; of air for icomlmstiomthe atdifferent mates ofoutput of said, apparatus; having in'combination --a plurality ofindices; mechanical. devices operating said i.ndi.ces;- mea-nsconnecting saidmechanical devices to-usaid apparatus. for causing-thedifferentialpressures that are respectively functions .ofsaid rateofsteam output and of said. rate of supply of -air= to act upon saiddevices; and meanscorrelating said devices and said indices forcausingsaid. indices to point to a commongraduation when-the de siredrelation exists. a

7. An instrument for showing whether-.01 not a certain desired relationexists between twoor more differently varying vfactors, which consistsof 'severalmechanical devices, each of which is operated upon by a forcecontrolled byand which isa function of one of said factors and. meanscorrelating said devices to cause/them to. show-the same readings whenthe said desired relation exists,

, regardless of the .actualvalues ofthefa-ctors.

8. 'An instrument for showing. whether or not a certain desiredvrelationexists between two or more differently varying factors, which consistsof mechanical devices having indices each-of which devices. isoperatedon by a force controlledbyand whichis a function of one of saidfactors respectivelyi,;-and means correlating said devices to operatesaid indices in unison and coextensively when the said relation exists:for any value of the principal factor.

; all rates-ofoutput when the condition oft-he desired efficiencyexists, relation between saidratesdlfterlng in value aneans for.continuously recording the po 9. An instrument; for showing whether ornot a certain desired relation exists between two or more differentlyvarying factors, of a power producing or using apparatus, whichinstrument consists of twoor more mechanical devices each having anindex; means whereby each of said devices is operated on by aforcecontrolledby and which isa functionxof oneof said factors; meanscorrelating said devices whereby they operate said indices in unison andcoextensively when the said relation exists throughout the-range ofoutput of the, apparatus; and means for recording the existence ornon-existence of said desired relation. 80

10; The herein described instrument for use in connection avith apower-producing or using apparatus, which consists of -,a mechanical(lGVlCQgxWlllCll is operated in re sponse to some forcecontrolled by andwhich varies as some function; ofthe rate atwhich energy is arsed bytheapparatus; another mechanicall device cwhich is operated in response tosome force, which Tvarie's'as some function of the rate ofwork doneindices operated by said devices respectively; and means correlatingsaid devices whereby the indices operated,-.b v =th em show readingsbearing-the same relation to oneanothcr at 11. The herein describedinstrument for use in connection with a power apparatus which consistsof a mechanicaldevice, which is operated in. responsetosome force, whichvaries as somefunctionof the rateat which energy. isjused qby th e::apparatns; another done indiceszmeans correlating ,said 1 devices to,operate said indices in unison-iand coextensively when ;the ;des ired,efficiency condition exists at iall rates-of output; and

sitionsof said indices;-

12, "The herein described instrument for giving, a ready comparison ofthe-important 1 factors which enterin'to the operation of a steamgenerat ng apparatus, which consists response to variations in the rateof supply of air for combustion; and means correlatmg, said elements sothat the same relatlve readin is shown b both indices when the airsupply is in the desired relation to ithei V steam output at; any, andall ratesvofoutput.

13. An instrument comprising two mechanical dev1ces, wh1ch are operatedby forces, controlled byand being functions of the rate offiow of steamfroma boiler, and

of the rate of the supply of air to the boiler furnace, respectively;indices; and means correlating said devices to operate said indices inunison and coextensively at all rates of output when the relationbetween the rate of How of steam and the rate of supply of air is thatwhich exists when the apparatus is operating at its best efficiency.

14. The herein described relation indicator, which consists of apressure gage having an index; a second pressure gage having an index;and means correlating the action of said pressure gages, whereby bothindices will bear the same relation to one another at all rates ofoutput of the apparatus to which said indicator is applied when thedesired relation exists between said pressures.

15. The herein described relation indicator, which consists of apressure gage having a pen cooperating with a chart; a second pressuregage having a pen also cooperating with said chart; and means wherebythe actions of said pressure gages may be correlated, so that both penswill give the same relative reading and substantially coincident recordson the chart, so long as the relation between the pressure ditierencesis as desired, at all rates of output of the apparatus to which saidindicator is applied, regardless of the actual value of one of saidpressure differences.

16. The herein described relation indicator which consists of a pressuregage having a pen cooperating with a chart; a second pressure gagehaving a pen also cooperating with said chart; means whereby the actionsof said pressure gages may be correlated so that both pens will give thesame reading and substantially coincident records on the chart when therelation between the pressure fll'lTElQHCGS is as desired, regardless ofthe actual values of said pressure differences; a pressure relation gageprovided with a pen also cooperating with said chart; and meansincorporated in said pressure relation gage for maintaining the said penstationary in a predetermined position relative to the chart so long asthe relation between the pressures remains as desired, regardless of theactual values of said pressures.

In testimony whereof, I have signed my name to this specification in thepresence of two subscribing witnesses.

ERVIN G. BAILEY.

WVitnesses J AS. J. MALoNEY, M. S. MALONEY.

Copies 0! this patent may be obtained {or five cents each, by addressingthe Commissioner of Patents,

Washington, D. C.

